N-acetylmuramyl-L-alanyl-D-isoglutamine or muramyl dipeptide (MDP) has been shown to be the smallest fragment of the bacterial cell wall capable of acting as an immune adjuvant. The purpose of this project is to chemically synthesize a series of MDP analogs and elucidate their host responsive properties. These compounds will be evaluated in vivo for toxicity, pyrogenicity, tumor regressive properties, as well as protection against airborne infection with influenza virus and virulent tubercle bacilli.